Add driver bpf hook for early packet drop

This patch set introduces new infrastructure for programmatically
processing packets in the earliest stages of rx, as part of an effort
others are calling Express Data Path (XDP) [1]. Start this effort by
introducing a new bpf program type for early packet filtering, before even
an skb has been allocated.

With this, hope to enable line rate filtering, with this initial
implementation providing drop/allow action only.

Patch 1 introduces the new prog type and helpers for validating the bpf
program. A new userspace struct is defined containing only len as a field,
with others to follow in the future.
In patch 2, create a new ndo to pass the fd to support drivers. 
In patch 3, expose a new rtnl option to userspace.
In patch 4, enable support in mlx4 driver. No skb allocation is required,
instead a static percpu skb is kept in the driver and minimally initialized
for each driver frag.
In patch 5, create a sample drop and count program. With single core,
achieved ~14.5 Mpps drop rate on a 40G mlx4. This includes packet data
access, bpf array lookup, and increment.

Interestingly, accessing packet data from the program did not have a
noticeable impact on performance. Even so, future enhancements to
prefetching / batching / page-allocs should hopefully improve the
performance in this path.

[1] https://github.com/iovisor/bpf-docs/blob/master/Express_D...

Brenden Blanco (5):
  bpf: add PHYS_DEV prog type for early driver filter
  net: add ndo to set bpf prog in adapter rx
  rtnl: add option for setting link bpf prog
  mlx4: add support for fast rx drop bpf program
  Add sample for adding simple drop program to link

 drivers/net/ethernet/mellanox/mlx4/en_netdev.c |  61 ++++++++++
 drivers/net/ethernet/mellanox/mlx4/en_rx.c     |  18 +++
 drivers/net/ethernet/mellanox/mlx4/mlx4_en.h   |   2 +
 include/linux/netdevice.h                      |   8 ++
 include/uapi/linux/bpf.h                       |   5 +
 include/uapi/linux/if_link.h                   |   1 +
 kernel/bpf/verifier.c                          |   1 +
 net/core/dev.c                                 |  12 ++
 net/core/filter.c                              |  68 +++++++++++
 net/core/rtnetlink.c                           |  10 ++
 samples/bpf/Makefile                           |   4 +
 samples/bpf/bpf_load.c                         |   8 ++
 samples/bpf/netdrvx1_kern.c                    |  26 +++++
 samples/bpf/netdrvx1_user.c                    | 155 +++++++++++++++++++++++++
 14 files changed, 379 insertions(+)
 create mode 100644 samples/bpf/netdrvx1_kern.c
 create mode 100644 samples/bpf/netdrvx1_user.c

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2.8.0